The present invention relates to a method and apparatus for weakening a portion of a web.
Many types of consumer goods are produced with a weakened region, such as a perforation, that allows a user to separate one portion of the good from another. For example, paper towels and toilet paper are typically provided with perforations that allow the user to separate one or more towels or sheets of tissue from a roll thereof. Likewise, many types of paper forms and computer paper have continuous webs of material that can be separated into one or more distinct, separate pages by breaking a weakened region thereof, for example a perforation. Similarly, plastic wrap and bags often are provided with perforations allowing the wrap to be torn, or a bag to be separated from a roll of such bags.
Typically, the types of consumer goods mentioned above are manufactured on a continuous basis on large scale manufacturing lines. Usually, various raw products or components are formed on, or integrated into, a continuous stream of material, which often includes a web of material that moves in a machine direction through and along the line. As such, it is important to maintain the integrity of the stream of material or web and minimize breaks thereof during the process so as to avoid costly downtime. In general, however, the web is pushed or pulled along the line, so as to put the web in tension. Accordingly, the formation of regions of weakness, especially along a cross-direction, can increase the risk of breakage. Therefore, it is desirable to maximize the tensile strength of the stream of materials or web as it passes through the process. At the same time, it is desirable for the end user to be able to break the various regions of weakness without undue effort, especially for people with reduced hand strength or dexterity, as can be caused, for example, by arthritis. Accordingly, there remains a need for maximizing the tensile capabilities of a stream of material or web across a weakened region during the processing of the consumer good, but also for minimizing the tensile capabilities across that same weakened region in the end product.
In other situations, the stream of material or web is weakened and then broken downstream, for example by accelerating the web on one side of the weakened region, often near the end of the process where the discrete products or goods are then acted on individually. Such methods and apparatus, however, typically require complex and expensive components to effect the timely acceleration and deceleration of the web. Accordingly, there also remains a need to provide a simple and effective way to break a web at a weakened region.